

1905.] Substance in Serum which influences Phagocytosis. 515 
what occurs in the case of agglutination, only the very strongest agglutinating 
sera would be regarded as giving positive results if 15 minutes were put as 
the limit of time for the serum to act on the microbes. 
_ As has been shown by the experiments quoted, the fall in the curve does 
not indicate complete destruction of the substance, as was stated by Bulloch 
and Atkin, but merely indicates that the substance has reached a concen- 
tration below that demonstrable by Wright and Douglas’ method. 
This view is emphasised by the experiment detailed in the following 
section. 
Effect of Continued Heating on the Substance in Serwm. 
Two series were prepared with normal horse serum heated at 60°C. for different periods. 
In each tube 1 c.c. of the heated serum was placed, and to the tubes of the one series 
0°08 c.c., to those of the other 0°05 c.c., of a coccal emulsion was added. The mixtures in 
each case were put for 15 minutes at 37°, then centrifugalised, and the centrifugalised 
cocci tested in the usual way. In most cases the leucocytes had to be noted simply as full, 
but where an obvious fall in the number of ingested cocci was observed, an enumeration 
was made. 
Mee hich -centin was Tubes to which 0°08 e.c. Tubes to which 0°05 c.e. 
qi 6 coccal emulsion added. coccal emulsion added. 
eated at 60° C. Nouutieccu: 1 e 
o. of cocci per leucocyte. | No. of cocci per leucocyte. 
20 minutes Full Full 
40 ,, Full Full 
60. ,, Full Full 
2 hours 36 Full 
ae 30 44 
hee 30 21 
This experiment proves that normal horse serum after being heated for 
four hours at 60° C. still contains enough of the substance to prepare a large 
number of the cocci for phagocytosis. With the quantities of coccal emulsion 
employed in this experiment a fall was observable with the larger quantity 
only after two hours’ and with the smaller quantity after three hours’ heating. 
On the Influence of Temperature on the Rate of Combination between the 
Substance and the Cocct. 
0'1 c.c. of an emulsion of Staphylococcus was added to 2 ¢.c. of normal human serum, 
which had been heated to 60° C. for 25 minutes. The emulsion was at once divided into 
two parts, and one part placed at 37° C., and the other at about 6—8° C., in the ice-chest. 
At the end of half an hour they were centrifugalised, the centrifuge buckets having been 
cooled down. The centrifugalised cocci in the two cases were then tested. 
